Address of dllimport function isn't considered constant expression by clang-cl

...causing the (mis-)use of std::integral_constant to fail with

> In file included from ucb/source/ucp/webdav-curl/CurlUri.cxx:20:
> In file included from ucb/source/ucp/webdav-curl/CurlUri.hxx:24:
> In file included from C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\memory:11:
> In file included from C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\exception:12:
> In file included from C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\type_traits:12:
> In file included from C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\xstddef:11:
> In file included from C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\cstddef:13:
> C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\xtr1common(22,26): error: constexpr variable 'value' must be initialized by a constant expression
>     static constexpr _Ty value = _Val;
>                          ^       ~~~~
> C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\xtr1common(28,16): note: in instantiation of static data member 'std::integral_constant<void (*)(void *), &curl_free>::value' requested here
>         return value;
>                ^
> C:/PROGRA~1/MIB055~1/2022/Preview/VC/Tools/MSVC/1430~1.307/Include\memory(3195,13): note: in instantiation of member function 'std::integral_constant<void (*)(void *), &curl_free>::operator void (*)(void *)' requested here
>             _Mypair._Get_first()(_Mypair._Myval2);
>             ^
> ucb/source/ucp/webdav-curl/CurlUri.cxx(49,25): note: in instantiation of member function 'std::unique_ptr<char, std::integral_constant<void (*)(void *), &curl_free>>::~unique_ptr' requested here
>     CurlUniquePtr<char> pPart2(pPart);
>                         ^

etc. as the involved functions like curl_free are defined as

  CURL_EXTERN void curl_free(void *p);

in workdir/UnpackedTarball/curl/include/curl/curl.h, where CURL_EXTERN expands
to __declspec(dllimport)

Change-Id: Ib278cd9e97260b588144d81dba344ccbb5309608
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/124899
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

4 files changed, 29 insertions, 22 deletions

diff --git a/ucb/source/ucp/webdav-curl/CurlSession.cxx b/ucb/source/ucp/webdav-curl/CurlSession.cxx
index 7cab4ca763ee..f407ad1e7435 100644
--- a/ucb/source/ucp/webdav-curl/CurlSession.cxx
+++ b/ucb/source/ucp/webdav-curl/CurlSession.cxx
@@ -776,7 +776,8 @@ struct CurlProcessor
     static auto ProcessRequest(
         CurlSession& rSession, CurlUri const& rURI, ::std::vector<CurlOption> const& rOptions,
         DAVRequestEnvironment const* pEnv,
-        ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pRequestHeaderList,
+        ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>>
+            pRequestHeaderList,
         uno::Reference<io::XOutputStream> const* pxOutStream,
         uno::Reference<io::XInputStream> const* pxInStream,
         ::std::pair<::std::vector<OUString> const&, DAVResource&> const* pRequestedHeaders) -> void;
@@ -792,10 +793,10 @@ struct CurlProcessor
                            ::std::u16string_view rDestinationURI, DAVRequestEnvironment const& rEnv,
                            bool isOverwrite, char const* pMethod) -> void;
 
-    static auto
-    Lock(CurlSession& rSession, CurlUri const& rURI, DAVRequestEnvironment const* pEnv,
-         ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pRequestHeaderList,
-         uno::Reference<io::XInputStream> const* pxInStream)
+    static auto Lock(CurlSession& rSession, CurlUri const& rURI, DAVRequestEnvironment const* pEnv,
+                     ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>>
+                         pRequestHeaderList,
+                     uno::Reference<io::XInputStream> const* pxInStream)
         -> ::std::vector<::std::pair<ucb::Lock, sal_Int32>>;
 
     static auto Unlock(CurlSession& rSession, CurlUri const& rURI,
@@ -1110,7 +1111,8 @@ static auto TryRemoveExpiredLockToken(CurlSession& rSession, CurlUri const& rURI
 auto CurlProcessor::ProcessRequest(
     CurlSession& rSession, CurlUri const& rURI, ::std::vector<CurlOption> const& rOptions,
     DAVRequestEnvironment const* const pEnv,
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pRequestHeaderList,
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>>
+        pRequestHeaderList,
     uno::Reference<io::XOutputStream> const* const pxOutStream,
     uno::Reference<io::XInputStream> const* const pxInStream,
     ::std::pair<::std::vector<OUString> const&, DAVResource&> const* const pRequestedHeaders)
@@ -1448,7 +1450,7 @@ auto CurlProcessor::PropFind(
                   != (::std::get<2>(*o_pRequestedProperties) != nullptr));
 
     // TODO: either set CURLOPT_INFILESIZE_LARGE or chunked?
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, "Transfer-Encoding: chunked"));
     if (!pList)
     {
@@ -1603,7 +1605,7 @@ auto CurlSession::PROPPATCH(OUString const& rURIReference,
     CurlUri const uri(CurlProcessor::URIReferenceToURI(*this, rURIReference));
 
     // TODO: either set CURLOPT_INFILESIZE_LARGE or chunked?
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, "Transfer-Encoding: chunked"));
     if (!pList)
     {
@@ -1791,7 +1793,7 @@ auto CurlSession::PUT(OUString const& rURIReference,
     CurlUri const uri(CurlProcessor::URIReferenceToURI(*this, rURIReference));
 
     // TODO: either set CURLOPT_INFILESIZE_LARGE or chunked?
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, "Transfer-Encoding: chunked"));
     if (!pList)
     {
@@ -1833,7 +1835,7 @@ auto CurlSession::POST(OUString const& rURIReference, OUString const& rContentTy
     CurlUri const uri(CurlProcessor::URIReferenceToURI(*this, rURIReference));
 
     // TODO: either set CURLOPT_POSTFIELDSIZE_LARGE or chunked?
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, "Transfer-Encoding: chunked"));
     if (!pList)
     {
@@ -1881,7 +1883,7 @@ auto CurlSession::POST(OUString const& rURIReference, OUString const& rContentTy
     CurlUri const uri(CurlProcessor::URIReferenceToURI(*this, rURIReference));
 
     // TODO: either set CURLOPT_POSTFIELDSIZE_LARGE or chunked?
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, "Transfer-Encoding: chunked"));
     if (!pList)
     {
@@ -1929,7 +1931,7 @@ auto CurlProcessor::MoveOrCopy(CurlSession& rSession, OUString const& rSourceURI
 
     OString const utf8Destination("Destination: "
                                   + OUStringToOString(rDestinationURI, RTL_TEXTENCODING_ASCII_US));
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, utf8Destination.getStr()));
     if (!pList)
     {
@@ -1983,7 +1985,8 @@ auto CurlSession::DESTROY(OUString const& rURIReference, DAVRequestEnvironment c
 
 auto CurlProcessor::Lock(
     CurlSession& rSession, CurlUri const& rURI, DAVRequestEnvironment const* const pEnv,
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pRequestHeaderList,
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>>
+        pRequestHeaderList,
     uno::Reference<io::XInputStream> const* const pxRequestInStream)
     -> ::std::vector<::std::pair<ucb::Lock, sal_Int32>>
 {
@@ -2095,7 +2098,7 @@ auto CurlSession::LOCK(OUString const& rURIReference, ucb::Lock /*const*/& rLock
     xRequestOutStream->closeOutput();
 
     // TODO: either set CURLOPT_INFILESIZE_LARGE or chunked?
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, "Transfer-Encoding: chunked"));
     if (!pList)
     {
@@ -2168,7 +2171,7 @@ auto CurlProcessor::Unlock(CurlSession& rSession, CurlUri const& rURI,
     }
     OString const utf8LockToken("Lock-Token: <"
                                 + OUStringToOString(*pToken, RTL_TEXTENCODING_ASCII_US) + ">");
-    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+    ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
         curl_slist_append(nullptr, utf8LockToken.getStr()));
     if (!pList)
     {
@@ -2206,7 +2209,7 @@ auto CurlSession::NonInteractive_LOCK(OUString const& rURI, ::std::u16string_vie
     try
     {
         CurlUri const uri(rURI);
-        ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist_free_all>> pList(
+        ::std::unique_ptr<curl_slist, deleter_from_fn<curl_slist, curl_slist_free_all>> pList(
             curl_slist_append(nullptr, "Timeout: Second-180"));
 
         assert(!rLockToken.empty()); // LockStore is the caller
diff --git a/ucb/source/ucp/webdav-curl/CurlSession.hxx b/ucb/source/ucp/webdav-curl/CurlSession.hxx
index 706aa54c19e5..563f7c3675dd 100644
--- a/ucb/source/ucp/webdav-curl/CurlSession.hxx
+++ b/ucb/source/ucp/webdav-curl/CurlSession.hxx
@@ -42,9 +42,9 @@ private:
     ::std::atomic<bool> m_AbortFlag;
 
     /// libcurl multi handle
-    ::std::unique_ptr<CURLM, deleter_from_fn<curl_multi_cleanup>> m_pCurlMulti;
+    ::std::unique_ptr<CURLM, deleter_from_fn<CURLM, curl_multi_cleanup>> m_pCurlMulti;
     /// libcurl easy handle
-    ::std::unique_ptr<CURL, deleter_from_fn<curl_easy_cleanup>> m_pCurl;
+    ::std::unique_ptr<CURL, deleter_from_fn<CURL, curl_easy_cleanup>> m_pCurl;
 
     // this class exists just to hide the implementation details in cxx file
     friend struct CurlProcessor;
diff --git a/ucb/source/ucp/webdav-curl/CurlUri.cxx b/ucb/source/ucp/webdav-curl/CurlUri.cxx
index 05b1892e6cf1..533a77606f47 100644
--- a/ucb/source/ucp/webdav-curl/CurlUri.cxx
+++ b/ucb/source/ucp/webdav-curl/CurlUri.cxx
@@ -238,7 +238,8 @@ void CurlUri::AppendPath(::std::u16string_view const rPath)
 
 CurlUri CurlUri::CloneWithRelativeRefPathAbsolute(OUString const& rRelativeRef) const
 {
-    ::std::unique_ptr<CURLU, deleter_from_fn<curl_url_cleanup>> pUrl(curl_url_dup(m_pUrl.get()));
+    ::std::unique_ptr<CURLU, deleter_from_fn<CURLU, curl_url_cleanup>> pUrl(
+        curl_url_dup(m_pUrl.get()));
     sal_Int32 indexEnd(rRelativeRef.getLength());
     auto const indexQuery(rRelativeRef.indexOf('?'));
     auto const indexFragment(rRelativeRef.indexOf('#'));
diff --git a/ucb/source/ucp/webdav-curl/CurlUri.hxx b/ucb/source/ucp/webdav-curl/CurlUri.hxx
index 2c7980176718..c9e8d33d279d 100644
--- a/ucb/source/ucp/webdav-curl/CurlUri.hxx
+++ b/ucb/source/ucp/webdav-curl/CurlUri.hxx
@@ -29,14 +29,17 @@
 
 namespace http_dav_ucp
 {
-template <auto fn> using deleter_from_fn = ::std::integral_constant<decltype(fn), fn>;
-template <typename T> using CurlUniquePtr = ::std::unique_ptr<T, deleter_from_fn<curl_free>>;
+template <typename T, auto fn> struct deleter_from_fn
+{
+    void operator()(T* p) const { fn(p); }
+};
+template <typename T> using CurlUniquePtr = ::std::unique_ptr<T, deleter_from_fn<T, curl_free>>;
 
 class CurlUri
 {
 private:
     /// native curl representation of parsed URI
-    ::std::unique_ptr<CURLU, deleter_from_fn<curl_url_cleanup>> m_pUrl;
+    ::std::unique_ptr<CURLU, deleter_from_fn<CURLU, curl_url_cleanup>> m_pUrl;
     /// duplicate state for quick access to some components
     OUString m_URI;
     OUString m_Scheme;